One in 12 hospital meals is returned uneaten, costing more than £22 million a year, according to figures from NHS trusts.
Analysis of data from 200 NHS hospital and mental health trusts suggests nine million meals (almost 8%) go back untouched every year across England.
Of 100 hospitals investigated by the watchdog, 49 resulted in minor, moderate or major concerns about nutrition, with hospitals frequently clearing trays before people got a chance to eat and elderly people not given help with their meals.
The data returns, examined by analysis specialist SSentif, found that Ipswich Hospital NHS Trust had the worst record, with 29% of meals returned uneaten.
At Cornwall Partnership NHS Foundation Trust (a mental health trust), 27% of meals are wasted, while 25% go uneaten at the University Hospital of South Manchester NHS Foundation Trust and 23% in Birmingham Women's NHS Foundation Trust.
At the other end of the scale, fewer than 1% of meals are returned uneaten at Buckinghamshire Healthcare NHS Trust, Oxford Health NHS Foundation Trust (a mental health trust) and Barnet and Chase Farm Hospitals NHS Trust.
Top of the list for how much it spends per patient, per day, on food is Kent and Medway NHS and Social Care Partnership (a mental health and learning disability trust), which says it spends £19 per patient, per day. At the bottom is Rotherham NHS Foundation Trust, which spends £2.93 per patient, per day.
The data suggests that high spend does not seem to equate with patients eating more meals: Ipswich spends £17.20 per patient, per day but has the highest proportion of meals sent back.
Judy Aldred, managing director of SSentif, said: "The fact that trusts spending a generous amount on hospital meals still report high percentages of meals being returned untouched would seem to suggest that the issue is less one of food quality and is more closely linked to protected patient mealtimes - either they aren't working or hospitals are failing to enforce them."
Health minister Simon Burns said: "Those hospitals with high levels of waste should be looking to learn from the ones that don't. All hospitals should also make sure that every patient gets the help they need to eat properly, and offer good quality, nutritious food. "